Fillament pulley does not fit

Today we started the assembly of our Vertex Nano 3d printer.
At step 10 of the instructions is says to “ Place the 1,75 FILAMENT PULLEY onto the extruder motor’s shaft.”
However, the pulley does not fit on to the shaft. I tried with another motor and is also did not fit on that motor shaft either.
Other pulleys fit fine.
Has anybody else encountered this issue? And/or does anybody have a suggestion to solve this?